1. Field
One embodiment of the invention relates generally to a disk drive device, particularly to a servo write technique of utilizing a multi servo spiral servo pattern to write a product servo pattern on a disk media.
2. Description of the Related Art
Generally, in a disk drive device such as a hard disk drive, a servo pattern (servo data) used in head positioning control (servo control) of a head is recorded on a disk media which is of a magnetic recording media.
In the disk drive, the head is positioned at a target position (target track) on the disk media using the servo pattern read by a read head included in the head. The read head performs an operation for reading data from the target position on the disk media. A write head included in the head performs an operation for writing data in the target position on the disk media.
The servo pattern is recorded on the disk media through a servo write process included in a disk drive production process. A self servo-writing method is receiving attention for the purpose of the efficient servo write process. In the self servo-writing method, the disk media in which a base pattern is previously recorded is incorporated in the disk drive, and the servo pattern is written on the disk media based on the base pattern using the head in the disk drive.
Recently, in the self servo-writing method, there is proposed a method in which plural spiral servo patterns are used as the base pattern to record a radial servo pattern on the disk media (for example, see U.S. Pat. No. 5,668,679 and U.S. Pat. No. 6,965,489).
The radial servo pattern is of the product servo pattern which defines concentric tracks. The radial servo pattern is of the servo pattern (sometimes referred to as final pattern) which is used in the head positioning control in the disk drive shipped as a product.
A burst signal into which sync marks are inserted at predetermined intervals is recorded in each spiral servo pattern. The burst signal is used to produce a position error signal. In the disk drive, the plural spiral servo patterns are used in a tracking (positioning) operation of the head.
Usually, in the case where plural radial servo patterns are written on the disk media by the self servo-writing method, the disk drive device is operated in synchronization with a servo write clock which is of a reference clock. Not only the servo write clock is used to write the radial servo pattern, but also the servo write clock is utilized as the reference clock for reading the spiral servo pattern.
Therefore, accuracy of the servo write clock becomes significant in order to accurately write the radial servo pattern on the disk media.